Three-piece, wound golf balls with balata (trans-polyisoprene) covers are typically preferred by professional and low handicap amateur golfers. These balls provide a combination of distance, high spin rate, and control that is not available with an ionomer cover or in one-piece and two-piece balls. However, balata cuts easily, and lacks the durability required by the average golfer.
Two-piece golf balls, which are typically used by the average amateur golfer, provide a combination of durability and maximum distance that is not available with balata covered balls. These balls comprise a core, formed of a solid sphere which typically comprises a polybutadiene based compound, encased in an ionomer cover formed of, e.g., SURLYN.RTM.. These ionomers are ionic copolymers of an olefin and an unsaturated carboxylic acid in which at least a portion of the carboxylic acid moieties have been neutralized with a metal ion; thus, these materials are referred to as carboxylated ionomers. These balls are extremely durable, have good shear resistance and are almost impossible to cut. However, the durability results from the hardness of the ionomer, which gives such balls a very hard "feel" when struck with a golf club that many golfers find unacceptable.
Golf ball manufacturers have attempted to produce golf ball covers that provide the spin rate of balata with the cut resistance of an ionomer by forming blends of carboxylated ionomers. However, none of the disclosed ionomer blends have resulted in the highly-desirable playability of a balata covered golf ball.
Several references disclose that sulfonated rubbers or elastomers may be used in golf ball covers. For example, Japanese patent publication JP 8-103516 A discloses a two layer golf ball with a cover formed only from the zinc ionomers of sulfonated non-polar rubbers, i.e., trans-polybutadiene, trans-polyisoprene or trans-polyoctenemer. These unsaturated rubbers are required to have at least 60% trans-1,4-configuration content and the added sulfonate moieties are said to be 100% neutralized with zinc in forming ionomers therefrom. However, this reference does not disclose or suggest that a polar rubber may be sulfonated and formed into an ionomer. Moreover, this reference does not disclose or suggest that a thermoplastic elastomer may be sulfonated and formed into an ionomer.
The JP reference neither discloses nor suggests that golf ball compositions comprising the ionomers described therein may be used in any layer of a golf ball other than the cover. Furthermore, this reference does not disclose or suggest that a sulfonated unsaturated rubber ionomer may be used in a blend with greater than 50 wt. % carboxylated ionomer in a golf ball composition. Additionally, this reference does not disclose or suggest that a sulfonated elastomer ionomer can be blended with a thermoplastic polymer such as a polyamide.
U.S. Pat. No. 5,679,745 to Hamada et al. discloses a two layer golf ball with a cover which comprises a mixture of a sulfonated ionomer and a carboxylated ionomer. This reference teaches that the sulfonated ionomer must have an elastomeric portion in the polymer chain; block copolymer elastomers comprising styrene and saturated hydrocarbon copolymer elastomers are said to be preferred. The Hamada et al. reference, however, does not disclose or suggest that a sulfonated elastomeric ionomer may be used without a carboxylated ionomer in a golf ball composition, nor does it suggest that a sulfonated elastomeric ionomer/carboxylated ionomer blend may be useful in any layer of a golf ball other than the cover. Additionally, this reference does not suggest that a sulfonated elastomeric ionomer can be blended with a polymer, such as a thermoplastic, which is not an ionomer; in particular, a sulfonated elastomeric ionomer blended with a polyamide is not disclosed.
Furthermore, neither of the above references discloses phosphonated ionomers or suggest that such materials could be present in golf ball compositions.
Other manufacturers have attempted to use nonionomer polymers, e.g., thermoplastics such as polyamide, in golf ball compositions to overcome the deficiencies in carboxylated ionomer blends. For example, U.S. Pat. No. 5,244,969 to Yamada discloses golf ball covers comprising a blend of two specific ethylene-acrylic acid copolymer ionomer resins and less than 20% by weight of a polyamide. Yamada does not claim or even disclose, however, a blend of a single carboxylated ionomer resin and a polyamide or the use of sulfonated and/or phosphonated ionomer blends with polyamide.
UK patent application GB 2299999 A discloses a three layer golf ball with a soft cover layer and a hard intermediate layer. The intermediate layer is said to contain at least 5% by weight of a high-rigidity polyamide resin, optionally blended with a carboxylated ionomer. Preferred polyamides are said to have a stiffness or bending modulus of 140 to 252 kpsi. The bending modulus of the intermediate layer composition is said to range from 56,000 to 112,000 psi, preferably 70,000 to 112,000 psi, while its Shore D hardness is said to range from 65 to 90. The cover layer of the three layer golf ball is said to comprise ionomer resin with a stiffness of 14,000 to 35,000 psi and Shore D hardness of 56 to 64.
The U.K. publication does not disclose sulfonated and/or phosphonated ionomers nor their blends with any polymer, such as a carboxylated ionomer or a non-ionomer polymer, including polyamides. It also does not disclose a blend of carboxylated ionomer/polyamide present in a cover layer, nor does it disclose a blend of carboxylated ionomer/polyamide present in an intermediate layer which is softer than the cover layer.
In all of the above references describing compositions comprising polyamide, none disclose or even suggest using blends of polyamide with sulfonated and/or phosphonated ionomers.
Several references disclose blends of sulfonated polystyrene ionomers and polyamide-6, e.g., see X. Lu and R. A. Weiss [Macromol., 25:6185-6189 (1992)]; Z. Gao et al. [Macromol., 25:6460-6465 (1992)]; R. A. Weiss and X. Lu [Polymer, 35(9):1963-1969 (1994)]; P. Rajagopalan et al. [J. Polym. Sci. Pt. B, Polym. Physics, 33:495-503 (1995)]. For example, P. Rajagopalan et al. disclose that blends of polyamide-6 and the lithium ionomer of 9.8 mol. % and 5.4 mol. % sulfonated polystyrene are miscible over a wide composition range. R. A. Weiss and X. Lu disclose that, in compatible sulfonated ionomer/polyamide blends, a complex forms between the metal sulfonate of a sulfonated polystyrene ionomer and the amide moiety of polyamide-6. Similar complexes are also thought to form between the lithium sulfonate of a sulfonated polystyrene ionomer and the amide moiety of poly(N,N'-dimethylethylene sebacamide) (a methylated polyamide); see R. A. Weiss et al. [ANTEC '97, 2653-2657 (1997)]. None of these references, however, disclose the use of such blends in golf balls. In addition, none of these references disclose a blend of a sulfonated ionomer formed from a non-styrenic polymer and a polyamide. Moreover, none of these references disclose an ionomer forned from a phosphonated polymer or a blend of a phosphonated ionomer with a non-ionomer polymer, e.g., a polyamide.
Several patents disclose blends of carboxylated ionomers and elastomers. For example, U.S. Pat. No. 4,858,924 to Saito discloses the use of a thermoplastic resin with a flexural modulus of 1,500 to 5,000 kg/cm.sup.2 as the cover of a golf ball. Particularly, polyamide elastomer, urethane elastomer, styrene-butadiene copolymer elastomer and polyester elastomer are said to be preferred when used alone or blended with a matrix resin, that is, another like flexible thermoplastic resin. The polyester elastomers are said to include block copoly(ether-esters), block copoly(lactone-esters) and aliphatic and aromatic dicarboxylic acid copolymerized polyesters. However, this reference does not teach that the ionomer blended with the polyamide can be formed from a sulfonated and/or phosphonated polymer.
U.S. Pat. No. 4,919,434 to Saito discloses the use of a carboxylated ionomer blended with a polyamide elastomer for use as the inner or outer cover of a golf ball. Described only as elastomeric, the polyamide elastomer material is said to have a low flexural modulus and hardness. However, the exact chemical composition or structure of the polyamide elastomer is not disclosed. When blended with a carboxylated ionomer, the polyamide elastomer-ionomer blend outer cover layer is said to have a flexural modulus of 28,000-71,000 psi (2000-5000 kg/cm.sup.2). However, Saito '434 is silent on the hardness characteristics of the blends and of their components. Moreover, Higuchi does not disclose blends of a polyamide elastomer with an ionomer formed from a sulfonated and/or phosphonated polymer.
Intermediate layers containing blends of carboxylated ionomers and elastomers are disclosed for multilayer golf balls. For example, U.S. Pat. No. 5,556,098 to Higuchi et al. discloses the use of a three-layer golf ball with a soft middle layer composed of a blend of a carboxylated ionomer and a polyamide elastomer, such that the JIS C hardness of the blend is less than 80. The exact chemical composition or structure of the polyamide elastomer is not disclosed other than that it is said to be a thermoplastic elastomer. However, Higuchi does not disclose blends of these elastomers with an ionomer formed from a sulfonated and/or phosphonated polymer.
U.S. Pat. No. 5,253,871 to Viollaz discloses the use of at least 10% of a block copoly(amide-ether) elastomer, optionally blended with a carboxylated ionomer, for use as the middle layer of a three-layer golf ball. The hardness of the block copolymer is said to be within the range of 30-40 Shore D hardness while the corresponding hardness of the ionomer component is said to be between 55-65 Shore D. The overall hardness of the middle layer is said to range from 20-50 Shore D. The cover may also be a block copoly(amide-ether) and ionomer blend but its overall hardness must be greater than that of the adjacent middle layer. However, Viollaz does not disclose blends of these block copolymers with an ionomer formed from a sulfonated and/or phosphonated polymer.
In all of the above references describing compositions comprising a polyamide elastomer, none disclose or even suggest, using blends of polyamide and sulfonated and/or phosphonated ionomers.
Carboxylated ionomers have been used in three component blends, as impact modifiers and/or as compatibilizers. For example, U.S. Pat. No. 4,840,982 to Campbell et al. discloses a blend containing a matrix (A) of an aromatic polymer (which may be polyamide, polyester, polycarbonate or polyimide but is preferably a polyphenylene ether or an aromatic polyester, polycarbonate or polyimide) in which is dispersed an impact modifier (B) consisting of a minor portion of a carboxylated or sulfonated elastomer (preferably an aliphatic hydrocarbon rubber) which is formed into an ionomer. A minor portion of a dispersion stabilizer (C) must also be present. (C) must be an aromatic polymer ionomer and, preferably, is an ionomer derivative of (A). This reference does not disclose the use of such blends in golf balls. Moreover, a blend comprising a phosphonated ionomer is not disclosed. Furthermore, a blend of a sulfonated ionomer and a non-aromatic polyamide is not disclosed. In addition, a blend consisting essentially of a sulfonated ionomer and a polyamide is not disclosed.
Compatibilizers consisting of carboxylated ionomers have been used to provide or enhance the compatible nature of blends of two non-ionomer polymers which are normally incompatible; see J. M. Willis et al. [J. Materials Sci., 26:4742 (1991)]; U.S. Pat. No. 4,801,649; EP 148,632 A2; and O. Olabisi [Encyclopedia of Chemical Technology, 3rd Edition, 18:474 (1982)]. A recent reference, U.S. Pat. No. 5,422,398 to Weiss, describes the use of a sulfonated polystyrene ionomer as a compatibilizer. Incorporation of this material into two incompatible heteroatom polymers, i.e., polymers comprising amide, ester, ether, sulfone or amine moieties, may result in a miscible blend. However, this reference does not disclose blends comprising a phosphonated ionomer, blends of a phosphonated ionomer and a non-ionomer polymer or blends consisting essentially of a sulfonated ionomer and a non-ionomer polymer. Moreover, the three component blends of this reference are not disclosed as being useful in golf balls.
U.S. Pat. No. 4,679,795 to Melvin et al. discloses blends of optical brighteners with the following golf ball cover materials: polyolefins and their copolymers; polyurethanes; polyamides; polyamide blends with SURLYN.RTM., polyethylene, ethylene copolymers and EPDM; acrylic resins; thermoplastic rubbers such as urethanes, styrene block copolymers, copoly(ether-amides) and olefinic thermoplastic rubbers; thermoplastic polyesters and polyester thermoplastic elastomers; and blends of thermoplastic rubbers with nylon. The reference contains no teaching or suggestion, however, to form a polyamide-sulfonated and/or phosphonated ionomer blend.
None of the blended compositions described above offers the combination of durability and distance provided by golf balls with ionomer covers and the high spin rate and control that is available with three-piece, wound golf balls having balata covers. Therefore, there remains a need for one-piece, two-piece, three-piece wound golf balls (with solid or liquid centers) and/or multilayer golf balls having cores, intermediate layers and/or covers comprised of an ionomer formed from a sulfonated and/or phosphonated polymer, with the durability and distance of a SURLYN.RTM. covered ball and the feel, click, and control of a balata covered three-piece ball.